Electric circuit breaker



May 23, 1939. 5 HOBSQN I 1 2,159,830

ELECTRIC C IRCUI T BREAKER Original F iled May 10, 1934 Inventor Lelahci 5. Hobson,

5 Atthhe Patented May 23, 1939 UNITED STATES PATIENT OFFICE ELECTRIC CIRCUIT BREAKER Leland S. Hobson, Yeadon, Pa., assignor to General Electric Company, a corporation of New York Claims.

My invention relates to electric circuit breakers of the fluid-break type wherein relatively movable contact structure is immersed in arc-extinguishing or insulating liquid, as oil, and has for 5 its principal object the provision of an improved circuit breaker of the aforesaid type which shall have appreciably increased interrupting capacity.

generation of gas by action of the are on the oil results in conducting gas bubbles of appreciable 29 volume at the breaks or points of contact separation tending to support arcing unless broken up sufiiciently by oil turbulence in the switch. The switch casing, which is but partially filled with oil, does not have a confining or restraining effect on the body of oil through which the bridging member descends with the result that the sudden generation of pressure upon opening of the circuit throws a large volume of oil upwardly into the air space of the switch casing. The region 30 adjacent the separating contacts is, therefore, but

partly filled with oil at the time when an insulating liquid is most needed. i Thebridging member may, therefore, be lowered varying distances in opening the circuit under similar load conditions before the insulating medium between the contacts has sufficient dielectric strength to interrupt the circuit at a current zero. Furthermore, if the circuit is not cleared when the bridging member reaches its lower limit of travel, failure of the breaker and a dangerous explosion and oil fire may result. In accordance with my invention, the interrupting capacity of the circuit breaker is'increased and greater reliability is obtained by improved baffle structure having a confining effect on the body of insulating liquid into which the movable contact structure is projected upon opening of the circuit, said baflle however being arranged so as to direct away from the contact structure the immediate escape of gas formed at each of the breaks.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the feature of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

This application is a division of my copendlng application Serial No. 724,864, filed May 10, 1934, for Electric circuit breakers.

Referring more particularly to the drawing, Fig. l is an elevational view, partly in section, of an oil circuit breaker embodying my invention, and Fig. 2 is a similar View showing a, modified form thereof.

The oil circuit breaker illustrated in Fig. 1 comprises a switch casing l formed by an oilcontaining tank 2 and a cover member or dome 3, and relatively movable contact structure t disposed within the casing and immersed in the 7 oil or insulating liquid 55. The contact structure may be of the well-known blade-and-flnger type,- the stationary contacts ti and l comprising spring mounted finger contact members arranged to be spread apart and interconnected, as illustratedby the. conducting bridging member 8. The stationary contacts and l are connected to and supported at the lower ends of the lead-in conductors 9 and ill which extend into the switch casing through the cover The lead-in con ductors i and it are supported by insulating bushings H and i2, respectively, and are suitably mechanically and electrically connected to the stationary contacts as by clamping means l3 and M, respectively.

Opening and closing of the circuit are effected by reciprocal vertical movement of the bridging member 8 which is connected to a lift-rod l5 in turn operatively connected to suitable actuating means (not shown) as fat IS. The oil circuit breaker structure so far described is conventional and opening of the circuit is effected simply by lowering the bridging member 8 within the oil body so that two breaks in series are formed between opposite ends of the bridging member and the arcing contact fingers 6' and I.

For the purpose of producing a restraining or confining effect on the oil body between the stationary contacts 6 and i, into which-the bridging member 8 is projected during the circuit opening operation, insulating baflle structure is employed. The battle also is arranged to provide immediate and direct escape of gas formed at both the contact breaks. In the present instance, I have illustrated a plate-like insulating baffle ll horizontally disposed beneath the surface of the oil 5 and immediately above the stationary contacts 6 and l in juxtaposition thereto. The insulating bafile I! is suitably composed of an impregnated laminated structure which is mechanically strong and of good insulating characteristics. With the exception of apertures l8 and is through which the lead-in conductor studs and lift rod [5 extend respectively, the baffle l'l between its outer edges is continuous between the stationary contacts and, although not illustrated, can fit closely against the end walls of the switch tank 2. By way of example, but without limitation thereto, a polyphase circuit breaker is preferred, the contact structure of the individual phases being similarly arranged beneath the baflie to operate simultaneously.

The baffle I1 at opposite edges is spaced from the side walls of the tank 2 to provide a venting passage immediately adjacent and opposite the breaks of each individual phase. As illustrated, the opposite edges of the baffle form with the tank walls a slot-like or rectangular passage between the upper and lower chambers defined by the baffle so as to afford direct and immediate escape of gas-formed at the contact breaks. The continuous portion of the baille prevents the main body of oil around the contact structure from being thrown into the air space of the switch casing. Accordingly, the bridging member in operation is lowered through a substantially uniform oil body instead of through a mixture of oil and gas as in the operation of the conventional plainbreak oil circuit breaker.

The immediate lateral escape of gas from the breaks at the opposite sides of the switch casing without appreciably disturbing the main oil body, therefore, not only eliminates a factor tending to cause prolonged arcing but also insures comparatively rapid interruption of the circuit by reason of the uniform oil body about the bridging member when the arc current passes through zero.

For the purpose of preventing expulsion of too great a quantity of oil beneath the baffle and also more effectively directing the escape of gas for are interruption, the insulating battle I! is provided with depending insulating structure com prising flanges 28 and 29 terminating adjacent the outer tips of the arcing contacts 6 and 1'. The flanges 28 and 29 are spaced, as illustrated, a suitable distance with respect to the side walls of the casing 2 so as to form rectangular chimney-like passages 28' and 29 for immediate and direct escape of the gas bubbles. It will be apparent that the cross-sectional area of the passages 28 and 29 may be varied to suit the operating requirements of the breaker. The present arrangement has the effect of bringing the bafile IT to a level adjacent the tips of the arcing contacts so that free gas enting is effected and a minimum amount of gas is present around the stationary contact structure upon opening of the circuit.

As previously described, le elimination and decrease in volume of the gas adjacent the separating contacts is highly desirable in order to increase the effectiveness of the insulating oil. In the present arrangement the main part of the oil body intermediate the lower tips of-the stationary contacts is not subject to displacement by the gas pressure; and the gas itself, under pressure, tends to expand directly into the exhaust passages 28' and 29'.

Fig. 2 illustrates an arrangement wherein an air or gas cushion is used generally for the purpose of absorbing in part and utilizing are energy in the case of heavy overload and short circuit currents. Excess energy initially absorbed can subsequently be" utilized to expel oil through the arc path. In this case the insulating baflle I1 is suitably positioned a short distance above the oil level so that an air space ll of the desired proportions is provided. For the purpose or defining the gas cushion and restraining the oil through which the bridge 8 is lowered, the bafile i1 is provided as in the previous case with depending flanges 28 and 29 which extend across the switch tank 2 so as to form with the sides thereof chimney-like passages 28' and 29' for the direct and immediate escape of gas from the breaks at 6' and 'I'.

The insulating flanges 28 and 29 preferably terminate approxima ly at the outer lower edges of the arcing contacts 6' and I as in Fig. 1. j

The air cushion at I1 is confined beneath the baiile structure and is so proportioned with respect to the interrupting capacity and operating requirements of the breaker that, no oil-throw takes place. The energy stored in the air cushion during circuit interruption is eifective, as above stated, to aid interruption of arcing at a current zero and to force out gas through the passages 28' and 29'.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising a casing containing an arc-extinguishing liquid, a pair of lead-in conductor studs extending within said casing, stationary arcing contacts mounted at the lower ends of said studs and immersed in said liquid, a movable bridging member coacting with said stationary contacts, and a horizontally disposed p1atelike insulating baille mounted at the lower ends of said studs and above said stationary contacts to form upper and lower chambers in said casing, said bafiie at opposite edges being spaced from the adjacent side walls of said casing to form a slot-like passage at each of said edges between said chambers for venting are gases at said stationary contacts, said baifie having de pending flange-like insulating structure at said opposite edges terminating approximately at a level defined by the lower edges of said stationary arcing contacts so that there is but a liquid-filled space between said bridging member and the adjacent side walls during opening movement of said member.

2. An electric circuit breaker comprising a casing containing an arc-extinguishing liquid, a pair of lead-in conductor studs extending within said casing, stationary arcing contacts mounted at the lower ends of said studs and immersed in said liquid, a movable bridging member coacting with said stationary contacts, and a horizontally dis- I posed plate-like insulating baille mounted at the the edges of said bafile opposite said side walls and terminating approximately at the outer lower edges of said stationary arcing contacts so that there is but a liquid-filled space between said bridging member and the adjacent side walls during opening movement of said member, said insulating flanges thereby defining with said side walls relief passages for the arc pressure generated beneath said bailie.

3. An electric circuit breaker comprising a casing containing an arc-extinguishing liquid, a pair of lead-in conductor studs extending within said casing, stationary arcing contacts mounted at the lower ends of said studs and immersed in said liquid, a movable bridging member co-acting with said stationary contacts,and a horizontally dis-- posed plate-like insulating baffle mounted at the lower end of said studs and above said stationary contacts, said baiile being generally of rectangular shape and engaging opposite end walls and spaced substantially equal distances from opposite side walls of said casing opposite said stationary contacts thereby forming rectangular shape lateral passages at the sides of the casing adjacent said contacts, said baflle at said lateral passages having a depending insulating flangelike structure at 'each edge terminating substantially at the level defined by the outer lower edges of said stationary arcing contacts, so that there is but a liquid-filled space between said bridging member and the adjacent side walls during opening' movement of said member.

4. An electric circuit breaker comprising a casing containing oil, a pair of lead-in conductor studs extending within said casing, stationary arcing contacts mounted at the lower ends of said studs and immersed in said oil, said stationary contacts being spaced substantially equal,dis-' tances from oppoflte side walls of said casing, a movable bridging member coacting with said stationary contacts, and a horizontally disposed plate-like insulating baffle corresponding approximately in width to the spacing between said arcing contacts mounted at the lower ends of said casing for venting arc gases generated at said arcing contacts beneath said batlie. 5. An electric circuit breaker of the fluid-break type comprising a casing partly filled with an arcextinguishing liquid, relatively movable contact structure immersedin said liquid including a pair of stationary contacts and a movable bridging member arranged to form two breaks in series, and an insulating baflle including a horizontally disposed plate-like portion above the level of said liquid, said baifle having oppositely disposed depending walls each spaced with respectto the side I walls of said casing to form passages opposite both of said breaks for directing immediate escape of the gas formed at said contacts upon opening of the circuit, said insulating balile thereby Iorming a substantially confined gas cushion above the level of said liquid and between said stationary contacts for aiding high current interruption.

. LELAND S. HOBSON. 

